Question: Simplify the following expression: $z = \dfrac{9}{10a} + \dfrac{-1}{10a}$
Solution: Since the expressions have the same denominator we simply combine the numerators: $z = \dfrac{9 - 1}{10a}$ Combine like terms: $z = \dfrac{8}{10a}$ Simplify by dividing numerator and denominator by 2: $z = \dfrac{4}{5a}$